The fate of a shrinking salt lake is the last thing you would expect football fans to chant about – but Iranians are doing all they can to stop a looming ecological disaster.

Lake Orumieh in north-west Iran, one of the world's largest salt lakes and a Unesco biosphere reserve, is disappearing due to drought and government mismanagement, and has become a major cause of concern for environmental activists and ordinary people in the Islamic republic.

Thousands of Iranians from Tabriz and Orumieh, two cities in Iran's Azerbaijan region, have come out on streets over the past few weeks in protest at the government's failure to protect the lake, which has already lost half of its surface in recent years. Lake Orumieh is situated at the heart of the region, home to the country's Azeri ethnic minority, whose activists claim they have been marginalised in recent years.

On Saturday security forces on motorcycles in Tabriz and Orumieh clashed with thousands of protesters who gathered in scattered groups raising alarms over the lake's disappearance. Experts have said the salt lake, crucial to agriculture and tourism, could dry out completely in the next few years.

Amateur videos posted on YouTube and social networking websites, believed to have been taken from Saturday's events, show riot police attacking what appears to be a peaceful protest. Opposition websites said riot forces wielded batons and used teargas and plastic bullets to disperse protesters who were chanting "Lake Orumieh is thirsty". Scores of protesters, including several environmental activists, have been arrested. The committee of human rights reporters in Iran reported on Monday that Farank Farid, a prominent women's rights activist, was among the protesters currently held in custody.

A website affiliated to South Azerbaijan's student movement claimed that protesters were injured in clashes with security forces. The association for defence of Azerbaijani political prisoners in Iran reported that eyewitnesses said at least one person was killed.

"According to the eyewitnesses, a protester was killed by the Iranian riot police in Tarbiat Street of the city of Tabriz. The body was immediately removed by the security forces," ADAPP said. The association reported protesters were chanting "Lake Orumieh is dying! Iran is issuing its execution", "Long live Azerbaijan".

Protesters blame the gradual drying of the salt lake on the government and its policies of damming rivers, but officials say drought and global warming has caused the disaster.

Some 36 dams have been built on rivers on the way to Lake Orumieh. Etemaad, a reformist newspaper, reported that the water level in Lake Orumieh falls by 3mm every day.

Experts say the government has refused to acknowledge the severity of the problem, which could have catastrophic environmental consequences. Fields of vine, almond and garlic in the region are dependant on Lake Orumieh. Experts say the intensity of the wind in the region would mean any salt left behind as the lake dries would destroy flora and fauna in the surrounding area, and also be harmful to humans.

Unable to stage street protests freely, Iranians have exploited every opportunity to voice alarm over the lake's fate. Football fans have chanted slogans in relation to the salt lake in stadiums since April. Activists are planning to stage another protest on Friday during a football match in Tehran's Azadi stadium, which holds up to 100,000 people.

Recent unrest in the Azarbaijan region saw familiar scenes to those witnessed in the aftermath of Iran's post-election protest in 2009.

Some analysts have seen these protests as being inspired by, and a continuation of, the unrest in 2009 and have even linked them to the uprisings in the Arab world. But there is little evidence to suggest recent events are connected to anti-regime movements.

Saturday's protests came after the Iranian parliament refused to fast-track a bid, proposed by local MPs, to feed the lake with water from a nearby river. Iran's semi-official Fars news agency published a letter, signed by 22 MPs, urging parliament to act on the issue. Speaking to Khabaronline, a news website, Javad Jahangirzadeh, an MP for the city of Orumieh, said: "In my view, the issue [of Lake Orumieh] should not be seen as a security issue and it should not be politicised. It is a social and environmental issue which we can rescue and it can be solved by the human."

He added: "Out of 100 people who come and visit me, 99 of them ask about Lake Orumieh, which shows it has become a sensitive issue for them. People follow the lake's fate, how can I stay silent and ignore their demands regarding an issue which shows their interest in the environment?"

Last year Iran's state television, Press TV, said the lake's problems were because "declining rainfall, climate change, and rising temperatures accelerate the evaporation process". were to be blamed.

Environmental experts fear that Lake Orumieh might see the fate of a lake in neighbouring countries, known as Aral Sea, which was formerly one of the four largest lakes in the world but has almost disappeared due to aggressive irrigation projects during the Soviet Union era.

Iranian media were not allowed to report from the protests but an official news agency acknowledged that a gathering had taken place on Saturday.

• This article was amended on 27 October 2011. The final sentence in the original said Iranian media were not allowed to 'report the protests'. This has been amended to 'report from the protests' to clarify the author intended to convey that on-the-ground reporting was barred; several follow-up articles about the action were published by Iranian media.